Les Atelier Cabinotiers is 'higher' than 'regular' VC's.
a) VC finishing is so high in their 'regular' models; that I find it hard to imagine if there is room to top it any more for Les Atelier Cabinotiers bespoke pieces.
b) For the first one or two stages of Les Atelier Cabinotiers, where you either have dial, case, or both modifications, VC is essentially placing an existing movement. So I am sure these movements come from their 'regular production line'.
c) For the lucky few who can commission their own movememnts, I still think that the finishing is as good as anything by VC. See a) above.
d) Its not about whether the finishing is better or not in the case of Les Atelier Cabinotier. The issue here is that you are an owner of a bespoke VC, which is 1/1. And that is the magical aspect.
I am writing as if I am an owner of a LCA piece, but I am not. Someday maybe. There are a few on the HL who have the privelige of this service and I am sure they will also write to your post.